R/V Atlantis Athena metadata file Wed 19/May/2004 23:38:34 Current time zone: GMT Standard Time ============================== GPS Navigation data (GPS) Complete NMEA data output from the primary GPS receiver. The single digit following the position information in the GPS_GGA data string indicates the type of GPS fix as follows: 0=No valid fix; 1=Standard; 2=Differential; 3=P-Code NMEA GPS_GGA data sentence: Header , UTC of position, Latitude, N/S, Longitude, E/W, Quality indicator, Number of satellites in use, Horizontal dilution, Altitude, M (meters), Geoidal seperation, M (meters), Age of differential data (secs), Differential reference station I.D. * checksum. The single digit following the position information (quality indicator) indicates the type of position fix: 0=No valid fix; 1=Standard; 2=Differential; 3=P-Code. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS course over ground (GPS_COG) Course over ground (true) obtained from NMEA GPS_VTG data sentence. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS speed over ground (GPS_SOG) Speed over ground (knots) obtained from NMEA GPS_VTG data sentence. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS type (GPS_TYPE) GPS position type (Std, Diff, P-Code) GPS position type indicator is obtained from the "quality indicator" included as part of the NMEA GPS_GGA data sentence. This value applies to the present primary GPS fix only and it is not necessarily an indication of the type of GPS receiver in use. See notes associated with the GPS data item. __________________________________________________ Gyro heading (Gyro) Format: Heading(degrees true) Ship's heading (degrees true) obtained from the HEHDT primary sensor. __________________________________________________ IMET Air Temperature (Air_Temp) Format: Temp (C) Data is obtained from IMET_HRH primary sensor. __________________________________________________ IMET Barometric Pressure (IMET_BPR) Format: Barometric pressure (milli-bars) Sensor installation dates: March 5, 2003 (Jacksonville, Fla.) __________________________________________________ IMET Humidity (IMET_HRH) Format: Humidity (%RH), Temperature (C) Note - IMET air temperature (Air_Temp) is obtained from this instrument. Sensor installation dates: March 5, 2003 (Jacksonville, Fla.) __________________________________________________ IMET Precipation (IMET_PRC) IMET_PRC Precipitation (millimeters) __________________________________________________ IMET Shortwave Radiation (IMET_SWR) Format: Radiation (watts/square meter) __________________________________________________ IMET Wind (IMET_WND) Format: X, Y, Total, Max, Min, LastVane, LastCompass, C1, C2 Wind X (m/sec), Positive for a stbd to port wind Wind Y (m/sec), Positive for a bow to stern wind Wind Total (m/sec), Averaged over previous minute Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (LastCompass should always be 0.0). Sensor installation dates: March 5, 2003 __________________________________________________ IMET relative humidity (HRH) Format: Humidity (%RH) Data is obtained from IMET_HRH primary sensor. __________________________________________________ Latitude (GPS_Lat) GPS_LAT GPS Latitude __________________________________________________ Longitude (GPS_Lon) GPS_LON GPS Longitude __________________________________________________ NMEA Gyro (HEHDT) Ship's heading obtained from the Sperry Gyro. NMEA format: Header ($HEHDT), Heading (degrees), T (true), Heading (degrees), M (magnetic) * checksum. Version 2.20 (1/1/97) of the NMEA 0183 standard does not show magnetic heading in this data sentence and the validity of this item is questionable. __________________________________________________ Position from GPS receiver (Lat_Lon) Format: decimal Latitude, N/S, decimal Longitude, E/W __________________________________________________ Salinity (Salinity) Format: Salinity calculated from SSTMP and SSCND data values in accordance with UNESCO 44. __________________________________________________ Sea Surface Conductivity (SSCND) Format: Sea surface conductivity (mmho/cm) Sensor installation dates: March 5, 2003 (Jacksonville, Fla.) __________________________________________________ Sea Surface Temperature (SSTMP) Format: Sea surface temperature (C) Falmouth Scientific Sensor installation dates: March 5, 2003 (Jacksonville, Fla) __________________________________________________ Sound velocity (SSV) Sea surface sound velocity (meters/second) calculated from SSTMP and SSCND data values. Intermediate salinity calculations are made in accordance with UNESCO 44. __________________________________________________ True wind direction (Wnd_Dir) Wind: * * * 01/31/96 Revision: * * * Wind Y (m/sec), Wind X (m/sec), Wind Total (m/sec), Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (value should always be 0.0). WHOI ship installation convention: "Wind Y" is positive for a stbd to port wind. "Wind X" is positive for a bow to stern wind. __________________________________________________ True wind speed (Wnd_Spd) Wind: * * * 01/31/96 Revision: * * * Wind Y (m/sec), Wind X (m/sec), Wind Total (m/sec), Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (value should always be 0.0). WHOI ship installation convention: "Wind Y" is positive for a stbd to port wind. "Wind X" is positive for a bow to stern wind. __________________________________________________ True wind speed & direction (TWind) __________________________________________________ Defined constants: WindSensorOffset = 0.0 __________________________________________________ Auxiliary information: Time stamp formats: Individual items in Athena ".dat" data files are time stamped with two different formats. The first time stamp value is in the format used by Microsoft Visual Basic: the number of days since December 31, 1899 (Dec. 31 is day 1, not day 0). Its primary purpose is to provide a continuously increasing date and time indicator for use in data graphing applications. The VB format facilitates this for some applications but converting the number to the normal human readable form can be painful. The second time stamp value (hh:mm:ss format) in combination with the file header's date information may eliminate the need for this conversion. If not, the following may be helpful: 00.00 is 00:00:00 on Dec. 30, 1899. 00.50 is 12:00:00 (noon) on the same day. 35390.58333 is 14:00:00 May 15, 1998.